As buildings get older, or as they suffer damage, they may require strengthening so as to avoid collapse, using, inter alia, masonry pinning and retrofit anchors. Such re-anchoring could be required due to poor brick tie configuration, wall tie deterioration, loosening walls, walls lacking lateral support or wall movement problems. Although expensive, reanchoring a brick veneer usually costs much less than removing and rebuilding the wall. Anchors or wall ties installed from the outside leave only small holes that are easily filled with color matched mortar or caulk. Wall ties are typically used to perform these tasks. Typically, wall ties perform three primary functions: provide a connection, transfer lateral loads, and permit in-plane movement to accommodate differential movements and, in some cases, restrain differential movement.
For a wall tie to fulfill these functions, it must be securely attached to the brick and masonry veneer and its backing, have sufficient stiffness to transfer lateral loads with minimal deformations, have a minimum amount of mechanical play, be corrosion-resistant and be easily installed to reduce installation errors and damage to the tie system.
Helical screw wall ties are known to be used as wall ties between brick and mortar veneers and studs. Typically, such helical screw wall ties consist of a steel rod having two ends, a helical screw portion on the first end and a bolt portion on the second end. When using a helical screw wall tie into a stud, three general types of anchors are used on the bolt end to anchor the wall tie to the mortar: adhesive; a mechanical expansion, or a nut assembly.
Most adhesive anchors are installed in similar ways, using an epoxy or polyester adhesive. First a hole is drilled, the drilling dust is removed, the helical screw wall tie is inserted into the hole and into the stud. A steel screen tube is filled with adhesive and the filled screen inserted in the hole. Inserting the steel screen over the steel rod pushes the adhesive through the screen into the pores of the masonry. This bonds the masonry and the steel rod together. Well known in the industry are both epoxy and polyester adhesives.
Mechanical anchors are also known as expansion anchors. To install an expansion anchor, a hole is drilled in the mortar joint. Once the helical screw is inserted into the stud, the expansion anchor is screwed onto the steel rod. The expansion anchor is torqued to be secured to the mortar. The torquing device is then removed Most mechanical anchors work by expanding a metal sleeve until the sleeve grips the inside of the drilled hole. In hollow masonry backups, the expanded sleeve may grip the back of the hole.
In the third type of anchor, a nut assembly, such as a nut and washer, toggle or the like, having a diameter greater than the hole is screwed onto the second end of the steel rod and torqued.
Regardless of the anchoring used, a disadvantage of the helical screw system is that the wood screw typically has a length longer than the stud into which it is screwed. Not only can this cause the wall tie to penetrate through interior finishes, a dangerous situation can develop if the helical end extends beyond the stud and into, e.g., electrical wires, flexible gas lines, and the like. What is desired is an improved wall tie that is adapted to avoid the damage and danger associated with a conventional helical screw wall ties.